Gas insulated switchgear used in electricity supply stations including substations and electric power plants is structured by disposing necessary devices such as switching devices, buses, current transformers, disconnectors, and voltage transformers, into a metal enclosure. The enclosure is hermetically closed after being filled with arc extinguishing gas such as sulfur hexafluoride (SF6) having excellent insulating and arc extinguishing properties. As a circuit type for gas insulated switchgear, a bus connection type using a so-called 1-½-Circuit-Breaker (CB) configuration is sometimes used in the case where it is necessary to have high reliability in, for example, substations having a large capacity. According to this type of bus connections, three circuit breakers having unit configurations are connected together in series between two main buses. In other words, the three circuit breakers are used for drawing out two lines in consideration that the system should not be affected even if an accident has occurred in any of the buses and that the lines should not have to be stopped when the circuit breakers and the like need to be inspected.
As an example of a conventional technique that uses such a 1-½-CB method, a piece of gas insulated switchgear is disclosed in, for example, Patent Document 1. In the example disclosed in Patent Document 1, three partial units are arranged side by side. Each of the partial units is structured by horizontally drawing out a current transformer and a disconnector in the same direction from a lateral face of a vertical-type circuit breaker while arranging one above the other with an interval therebetween. With regard to any two partial units that are positioned adjacent to each other, the lower disconnector included in one of the two partial units is connected to the upper disconnector included in the other of the two partial units by using a diagonal bus, so that the three partial units are connected together in series.
As another example, Patent Document 2 discloses an arrangement in which three partial units are arranged side by side. Each of the partial units is structured by horizontally drawing out a current transformer and a disconnector in the same direction from a lateral face of a vertical-type circuit breaker while arranging one above the other with an interval therebetween. On the drawn-out side of the devices, two main buses are provided so as to extend at substantially the same level in a lower layer below the disconnectors.
Patent Document 1: Japanese Patent Application Laid-open No. H6-62513
Patent Document 2: Japanese Patent Application Laid-open No. 11-341627